Selective fusing

ABSTRACT

Fuser regulating methods and the apparatus therefor are provided in accordance with the teachings of the present invention wherein a fuser assembly is selectively energized in accordance with the intermittent movement of successive portions of a support base through the fuser assembly such that said fuser assembly rapidly attains an operating temperature sufficient to fuse to said support base the electroscopic particles supported thereon. The fuser assembly is energized for a preestablished minimum period of time when successive portions of the support base are moved therethrough within a first time duration. The fuser assembly is energized for a second pre-established period of time greater than the minimum period of time when a first interval of time has expired since the immediately preceding energization thereof. If a second interval of time has expired since the immediately preceding energization of the fuser assembly, the assembly is energized for a third pre-established period of time when the next successive portion of the support base is advanced thereto. The second interval of time is greater than the first interval of time and the third pre-established period of time is greater than the second pre-established period of time. Further periods of energization may be established in accordance with the amount of time that has expired since an immediately preceding energization.

United States Patent [1 1 Hutner SELECTIVE FUSING [75] Inventor: Mark A.Hutner, Glenview, Ill.

[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

[22] Filed: Mar. 27, 1973 [21] Appl. No.: 345,384

[44] Published under the Trial Voluntary Protest Program on January 28,1975 as document no. B 345,384.

Related US. Application Data [62] Division of Ser. No. 221,193, Jan. 27,1972, Pat. No.

[52] US. Cl. 219/216 [51] Int. Cl. H05B 1/00; 6036 15/00 [58] Field ofSearch 219/216, 388;

[56] References Cited UNITED STATES PATENTS 3,398,259 8/1968 Tregay etal 219/216 3,445,626 5/1969 Michaels 219/501 X Primary Examiner-C. L.Albritton Attorney, Agent, or Firm-R. A. Stoltz [57] ABSTRACT Fuserregulating methods and the apparatus therefor are provided in accordancewith the teachings of the present invention wherein a fuser assembly isselectively energized in accordance with the intermittent movement ofsuccessive portions of a support base through the fuser assembly suchthat said fuser assembly rapidly attains an operating temperaturesufficient to fuse to said support base the electroscopic particlessupported thereon. The fuser assembly is energized for a preestablishedminimum period of time when successive portions of the support base aremoved therethrough within a first time duration. The fuser assembly isenergized for a second pre-established period of time greater than theminimum period of time when a first interval of time has expired sincethe immediately preceding energization thereof. If a second interval oftime has expired since the immediately preceding energization of thefuser assembly, the assembly is energized for a third pre-establishedperiod of time when the next successive portion of the support base isadvanced thereto. The second interval of time is greater than the firstinterval of time and the third preestablished period of time is greaterthan the second pre-established period of time. Further periods ofenergization may be established in accordance with the amount of timethat has expired since an immediately preceding energization.

6 Claims, 5 Drawing Figures TO SCANNING 6 QELECTION CIRCUIT U.S. Patent'Oct.28, 1975 Sheet2of3 3,916,146

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US. Patent Oct. 28, 1975 Sheet 3 (3 3,916,146

m mik IN Q\N h%N c o x86 2. 0Z 1 mow 3m 3w m v V m z m moz moz bow w L mh w u DON SELECTIVE FUSING This is a division, of application Ser. No.221,193, filed Jan. 27, 1972 now U.S. Pat. No. 3,743,779.

This invention relates to electroscopic fusing techniques and, moreparticularly, to a method of selectively regulating a fuser assembly andthe apparatus therefor.

Electrophotographic reproducing techniques of the type described indetail in U.S. Pat. No. 2,297,691 which issued to Chester F. Carlson,form electrostatic latent images of original documents by selectivelydissipating a uniform layer of electrostatic charges deposited on thesurface of a photoreceptor in accordance with modulated radiation imagedthereon. The electrostatic latent image thus formed is developed andtransferred to a support surface to form a final copy of an originaldocument. The development process is effected by applying electroscopicparticles, conventionally known as toners, to the electrostatic latentimage whereat such particles are electrostatically attracted to thelatent image in proportion to the amount of charge comprising suchimage. Hence, the areas of small charge concentration are developed toform areas of low particle density, while areas of greater chargeconcentration are developed to form areas wherein the particle densityis greater. Once transferred to the support surface, the developed imagemay be permanently fixed thereto by heat fusing techniques wherein theindividual particles soften and coalesce when heated so as to readilyadhere to the support surface.

Various modifications in fusing techniques have heretofore beendeveloped which achieve divers results, such techniques includingselective fusing. In selective fusing, toner areas admitting of a higherdensity are preferentially fused leaving low density or background areasunfused. Unfused toner particles comprising background can thenberemoved to yield a cleaner, more readable copy. Selective fusing alsocontemplates the irregular, non-continuous, non-periodic operation of afuser assembly in response to particular predetermined conditions. Inthis regard, selective fusing techniques are readily adapted tocooperate with selective xerographic printing techniques. Thus, ifcopies of only selected ones of successively scanned original documentsare to be printed, the fuser assembly must be energized each time adeveloped image of a selected original is transferred to the supportsurface. It is appreciated that if the support surface comprises a webof suitable material, such as paper, the web will be transported throughthe fuser assembly in an irregular manner corresponding to the scanningof the unique originals to be reproduced. Consequently, scorching orburning of the web that is stationarily disposed within the fuserassembly must be avoided, while, at the same time, sufficient heat mustbe accummulated in the assembly to assure an adequate fusingof the tonerareas to the Web.

In the implementation of either of the aforementioned selective fusingtechniques, i.e., the fusing of toners areas of a high density to theexclusion of relatively low density areas on a continuously movingsupport surface or the fixing of successive toner areas disposed inimage configurationupon an irregularly moving support surface, it hasbeen found, that in addition to the problem of scorching the supportsurface, it is necessary to provide for an intrinsic delay in raisingthe temperature of the fuser assembly to a proper value in response tothe energization thereof, the accumulation of heat within the assemblyduring the duration of energization thereof and the temperature to whichthe assembly has cooled in the time that has expired since theimmediately preceding energization thereof. An attendant disadvantage ofprior art selective fusing techniques if the failure of such techniquesto vary the amount of heat emitted by the fuser assembly in accordancewith the length of time such assembly has been permitted to cool. Anattempt to overcome this difficulty has resulted in maintaining thefuser assembly at a quiescent temperature level that, in some instances,has caused the scorching of the support surface disposed therein.

Therefore, it is an object of the present invention to provide a methodof and apparatus for selectively fusing electroscopic particles to asupport surface.

It is another object of the invention to provide a method of andapparatus for regulating the operation of a fuser assembly in accordancewith selected conditions requiring the energization of said assemblywherein the heat accumulated by the assembly is a function of theexpiration of time from an immediately preceding energization thereof.

A further object of the present invention is to provide a method offusing electroscopic particles to successive portions of a support baseintermittently moving through a fuser assembly, and the apparatustherefor.

An additional object of the present invention is to provide apparatusfor selectively energizing a heating element that is maintained at atemperature level no lower than a quiescent level for variable timedurations such that a substantially equal radiant energy level isattained thereby during each energization irrespective of the length oftime that has expired since an immediately preceding energizationthereof.

Still another object of this invention is to provide a method of rapidlyenergizing a fuser assembly to permit the fixing of toner particlesthereby, while precluding the possibility of scorching a support surfacedisposed therein, and the apparatus therefor.

Yet a further object of the present invention is to provide a method ofselectively energizing a fuser assembly, and the apparatus therefor, inaccordance with the amount of cooling to which said assembly has beensubjected.

Another object of this invention is to provide a method of and apparatusfor fusing electroscopic particles disposed in image configuration on asupport surface in accordance with the intermittent movement of saidsurface through a fuser assembly.

Various other objects and advantages of the invention will become clearfrom the following detailed description of an exemplary embodimentthereof, and the novel features will be particularly pointed out inconnection with the appended claims.

In accordance with this invention, there are disclosed fuser regulatingmethods and the apparatus therefor, wherein the fuser assembly isselectively energized in accordance with the occurrence of preselectedconditions such that the fuser assembly rapidly attains an operatingenergy level sufficient to fuse to a support surface the electroscopicparticles supported thereon; said fuser assembly being energized for apreestablished minimum duration of time when the immediately precedingenergization thereof occurred within a first time duration; and saidfuser assembly being energized for variable durations of timeinaccordance with the interval that has expired since the immediatelypreceding energization thereof.

The invention will be more clearly understood, by reference to thefollowing detailed description of an exemplary embodiment thereof inconjunction with the accompanying drawings in which: I

FIG. 1 is a schematic diagram of a typical selective printing apparatuswith which the instantinvention may be utilized;

FIG. 2A is a schematic diagram of a conventional heating element thatmay be utilized in the fuser assembly of FIG. 1 and variable supply ofenergy therefor;

FIG. 2B depicts an AC waveform that is helpful in explaining theoperation of the electrical circuit illustrated in FIG. 2A;

FIG. 3 is a schematic illustration of the logic circuitry that may beutilized to selectively regulate the variable supply of energy depictedin FIG. 2A; and

FIG. 4 depicts a timing diagram representing the voltage signalsproduced by the logic circuit of FIG. 3.

For a general understanding of selective printing apparatus in which theinstant invention may be incorporated, reference is made to FIG. 1 inwhich some of the various system components for the apparatus areschematically illustrated. Like component parts are identified by likereference numerals throughout and primed reference numerals identify thewaveforms produced by corresponding component parts identified byunprimed reference numerals. The printing apparatus illustrated hereinemploys electrophotographic concepts originally disclosed in U.S. Pat.No. 2,297,691, which issued to Chester F. Carlson. Accordingly, theselective printing apparatus comprises an electrostatic system wherein alight image of an original to be reproduced is projected onto thesensitized surface of a photosensitive plate to form an electrostaticlatent image thereon. Thereafter, the latent image is developed with anoppositely charged developing material comprising electroscopicparticles, known as toner particles, to form a powder imagecorresponding to the latent image on the photosensitive surface. Thepowder image is then electrostatically transferred to a support base towhich it may be fixed by a fusing assembly whereby the powder is causedto adhere permanently to the support surface.

In the illustrated apparatus, visible document information is providedon each of the data cards 1 that are successively transported from'afeeder tray 2 to a restack tray 49. The data cards are transported intimed sequence with respect to the operation of the remaining apparatusillustrated herein, and are caused to traverse detecting station A,scanning station B and slit exposure device 34 in successive order. Eachdata card is additionally provided wtih precoded information thereon,which precoded information is determinative of the selective printing ofthe visible document information carried by the card. More particularly,if the precoded information scanned from the card by scan ning station Badmits of a particular precondition, additional logic circuitry, notshown, responds to such scanned information to derive a print signal.The thus derived print signal is operated upon in a timed sequence toprovide a direct correspondence between the sequential manipulation ofsuch print signal and the particular operation performed by theapparatus illustrated in FIG. 1.

The sequential passage of data cards from the scanning station B throughthe projection system 33 to the restack tray 49 will cause opticalimages of the visible document information on each of the data cardspassing through the slit exposure device 34 to be sequentially projectedupon the surface of photosensitive drum 20. If desired, the projectedimages may admit of magnification. The photosensitive drum 20 iscontinuously driven at a constant angular velocity such that the surfacethereof is moving at a velocity equal to that of the data cards movingpast the exposure device 34. In moving in the direction indicated by thearrow, prior to reaching the exposure station C, that portion of thephotosensitive drum being exposed is uniformly charged by a coronadischarge station G.

The exposure of the photosensitive drum surface to the light imageselectively dissipates the electrostatic charge on the surface thereofin the areas struck by light, thereby forming an electrostatic latentimage in image configuration corresponding to the light image projectedfrom the visible document information on the data card transportedthrough the slit exposure device 34. As the photosensitive drum surfacecontinues its movement, the electrostatic image passes through adeveloping station D in whichthere is positioned a de veloping apparatusgenerally indicated by the reference numeral 13.

;,If the electrostatic latent image passing through development stationD is derived from a data card having a print signal associatedtherewith, such print signal is utilized to activate the developer motor24 such that the developing apparatus may be operated to develop suchelectrostatic latent image. In contradistinction thereto, should theelectrostatic latent image passing through the developing station D bederived from a data card not having a print signal associated therewith,the,developer motor 24 is not activated and such electrostatic latentimage is not developed. It is therefore appreciated that thedevel opingapparatus 13 is operated in an intermittent manner wherein only thoseelectrostatic latent images derived from data cards having printsignalsassociated therewith are developed at station D. Hence, as thephotosensitive drum 20 continues to rotate in the direction indicated bythe arrow, successive areas thereof will be provided with imageinformation distributed thereon in the form of a distributedelectrostatic charge pattern. However, only selected ones, of successiveareas will be developed. As illustrated herein, the developing apparatus13 may typically be provided with electroscopic particles that arecascaded across the surface of photosensitive drum 20, which particlesare attracted electrostatically to the distributed charge pattern toform powder images.

I The developed electrostatic image is transported by the photosensitivedrum 20 to a transfer station E located at a point of tangency on thephotosensitive drum whereat a support base 9 is intermittently moved ata speed in synchronism with the moving drum in order to accomplishtransfer of the developed image. The supportbase 9 is here depicted as aweb comprised of suitable material such as paper, plastic or the like,that is driven from a supply 13 through selective transfer mechanism 25,through fuser assembly 40, about strip driving means 16 and into a stripreceiving tray 14. At thetime a developed image having a print signalassociated therewith arrives at the transfer station E, theassociatedprint signal is operated upon to cause the web driving means16 to be activated, thereby transporting the support base 9 at avelocity equal to the surface velocity of the photosensitive drum 20.Moreover, the print signal is used to operate the selective transfermechanism 25 whereby the support base 9 engages the photosensitive drum20 in an arc of contact. In addition, charging means 30 may be energizedto provide a charge on the support base 9 prior to its engagement withthe photosensitive drum so that the developed image may beelectrostatically transferred from the surface of ,drum 20 to theadjacent side of the support base as such support base is brought intocontact therewith. Thus, it is seen, that each developed electrostaticimage is transferred to the support base 9; and the support base is,therefore, advanced in an intermittent manner in accordance with eachprint signal that is derived from the scanning information carried bythe transported data cards.

After transfer, the support base 9 is transported to the fuser assembly,generally indicated by the reference numeral 49, wherein the developedand transferred powder image on the support base is permanently fixedthereto. The fuser assembly 40 may comprise conventional apparatuscapable of carrying out various fusing techniques such as oven fusing,hot air fusing, radiant fusing, hot and cold pressure roll fixing andfusing and flash fusing. Merely for the purpose of explanation, it willbe assumed that the fuser assembly 40 is comprised of one or more quartzlamps connected in parallel relationship and shaped to emit a suitableamount of heat when energized. The dimensions of the assembly may besuch as to admit of a plurality of transferred images to be disposedtherein. Additionally, the fuser assembly is maintained at a quiescentoperating temperature when not energized, said quiescent operatingtemperature being slightly less than the temperature normally requiredto fix the powder image to prevent scorching to the support base. It is,therefore, readily apparent that the print signal derived from a datacard is operated upon in a preselected sequential manner incorrespondence with the transporting of a transferred image to the fuserassembly 40. Since, however, immediately succeeding areas of the supportbase 9 are provided with transferred images, but succeeding ones of thedata cards are not necessarily provided with the unique precodedscanning information, it is recognized that the support base is movedintermittently through the fuser assembly in an irregular manner.Consequently, the fuser assembly 40 must not be continuously energizedin order to avoid the scorching of the support base that is maintainedin a temporary stationary relationship with respect thereto.Nevertheless, as an immediately succeeding portion of the support baseis advanced to the fuser assembly, the latter must be rapidly energizedto an operating level capable of fixing the electroscopic powder imageupon the support base. The manner in which the fuser assembly 40 isregulated to provide the just-mentioned selective fusing is described indetail hereinbelow.

The excess electroscopic particles remaining as residue on the developedimages, as well as those particles not otherwise transferred therefrom,are carried by the photosensitive drum 20 to a cleaning station F on theperiphery of the drum adjacent the charging station G. The cleaningstation may comprise a rotating brush and a corona discharge device forneutralizing charges remaining on the nontransferred electroscopicparticles.

Various other configurations and components may comprise the cleaningstation F as is well-known to those of ordinary skill in the art.

A more complete description of the selective printing apparatusillustrated in FIG. 1, and the manner in which such apparatus operates,is set forth in detail in U.S. Pat. No. 3,700,324 issued Oct. 24, 1972and assigned to Xerox Corporation, the assignee of the instantinvention. It should, however, be clearly understood that the selectivefusing techniques to be described in detail hereinbelow are readilyadapted for broad application and should not be unnecessarily limited tothe specific system described above. It will, therefore, become readilyapparent that the instant invention may be readily utilized wheneverselected ones of original documents are to be reproduced. Statedotherwise, the selective fusing techniques described hereinbelow arereadily adapted to fix powder images to a support base therefor on anirregular basis in accor' dance with the occurrence of preselectedconditions. Thus, in addition to the selected use as described withrespect to FIG. 1, the selective fusing techniques of the presentinvention may be employed for the preferential fusing of dense imageareas while leaving low density or background areas unfused.

Turning now to the subject matter of the present invention, and inparticular, to FIGS. 2A and 28, there is schematically illustrated aconventional heating ele ment 105 that may be typically included in thefuser as sembly 40 of FIG. 1. The heating element 105, which maycomprise a plurality of quartz lamps connected in parallel relationship,is coupled to a variable supply of voltage, generally designated by thereference numeral 100, the latter being adapted to supply the heatingelement 105 with energy. The variable supply may be a conventionalvoltage regulator such as model 9T68Y7001 manufactured by GeneralElectric, and therefore need not be described in detail herein. Itshould however, be noted that the variable supply 100 includesbi-directional current conducting means 101 which may be a siliconbi-directional triode device, such as a triac, capable of conductingrelatively high AC current in both directions and whose time of initialconduction during a half cycle is dependent upon the magnitude of acontrol voltage applied to the trigger input 101a thereof. Hence, thebi-directional current conducting means 101 may function as atriggerable switch that is rendered conductive during a half cycle of anAC voltage applied thereto when the voltage exceeds a threshold orfiring level. Those of ordinary skill in the art will recognize that thebi-directional current conducting means may be a conventional thyrister.Once rendered conductive, the bi-directional current conducting means101 is adapted to remain conductive until the voltage applied theretocommences a successive half cycle.

It may be observed that the control voltage applied to the trigger input101a of bi-directional current conducting means 101 is derived from avoltage dividing means that comprises series connected resistance means102, 103 and 104. Trigger input 101a is coupled to the junction formedby the series connection of resis tance means 102 and 103. The value ofthe resistance of resistance means 102 is, to some degree, determined bythe intensity of radiant energy emitted by lamp 108 and, therefore, isprecisely regulated. In accordance with the present invention, thethreshold level at which the bi-directional current conducting means 101is tendered conductive, is decreased by selectively reducing the voltagederived by the illustrated voltage dividing means. Adjustable resistancemeans 106 is capable of being selectively connected in parallelrelationship with resistance means 102 by energizable switch 107. Itshould be appreciated that the effective resistance of the first stageof the illustrated voltage dividing means is'lde'creased when adjustableresistance means 106 is connected in parallel with resistance means 102.Consequently, the threshold or firing level voltage applied to thetrigger input 101a of bi-directional current conducting means 101 iscorrespondingly increased. Thus, the time of initial conduction during ahalf cycle is advanced and the duration of conductivity of thebidirectional current conducting means 101 is increased. With adjustableresistance means 106 connected in parallel with resistance means 102,the root mean square (RMS) voltage applied to heating element 105 isdecreased, resulting in a decrease in the amount of heat radiatedtherefrom. Adjustable resistance means 106 may comprise a conventionalpotentiometer, rheostat or the like whereby an adjustment of theresistance value thereof enables a corresponding adjustment in thethreshold or firing level of bi-directional current conducting means.Hence, a suitably wide range in the RMS voltage applied to heatingelement 105 may be obtained.

The manner in which the variable supply 100 is utilized to regulate theheat radiated by heating element 105 may be readily understood byreferring to FIG. 2B. Normally, the heating element 105 is maintained ata quiescent level of energization to radiate an amount of heat that isnot quite sufficient to fuse electroscopic material to a support base.Nevertheless, this quiescent energization enables the radiant energyemitted by the heating element to be rapidly increased to a properfusing level when the voltage applied to said heating element isincreased. When adjustable resistance means 106 is connected in parallelwith resistance means 102, a quiescent threshold level is applied totrigger input 101a of bi-directional current conducting means 101. Asillustrated in FIG. 23, this quiescent threshold level renders thebi-directional current conducting means conductive at a point on thepositive half cycle of the AC voltage applied to the bi-directionalcurrent conducting means defined by the intersection of broken line 121aand AC waveform 120. The bi-directional current conducting means 101 isrendered nonconductive at the conclusion of a positive half cycle.However, at a point on the negative half cycle defined by theintersection of broken line 121b and AC waveform 120, the bi-directionalcurrent conducting means is again rendered conductive. It is appreciatedthat when the quiescent threshold level is applied to trigger input 101aof bi-directional current conducting means 101, the bi-directionalcurrent conducting means is rendered conductive for only a relativelysmall portion of an AC cycle. This duration of conductivity, however issufficient to apply an RMS voltage to heating element 105 whereby theheating element is maintained at a quiescent level of energization.Should the RMS voltage applied to heating element 105 be increased, theheat radiated thereby will be sufficient to fuse electroscopic material.

When energizable switch means is energized so as to assume an openstate, adjustable resistance means 106 is thereby disconnected fromresistance means 102. It may be recognized that switch means 107 maycomprise the movable contact of a conventional relay, an electronicswitch or the'like. The disconnecting of adjustable resistance means 106from resistance means 102 alters the ratio of division of the voltagedividing means to thereby alter the threshold level applied to triggerinput 101a. Accordingly, the point at which the bi-directional currentconducting means 101 is rendered conductive during the positive halfcycle of the AC voltage applied thereto is defined by the intersectionof line 122a and AC waveform 120 illustrated in FIG. 2B. Theconductivity of the bi-directional current conducting means ismaintained until the conclusion of the positive half cycle. During thenegative half cycle of the AC voltage, bi-directional current conductingmeans 101 is rendered conductive at the point of intersection of line122b and AC waveform 120. The relatively large duration of conductivityduring each cycle is effective to apply an increased RMS voltage toheating element whereby the heat radiated by the heat ing element issufficient to fuse the electroscopic material. It should be readilyunderstood that if energizable switch means 107 is energized for aplurality of AC cycles, the amount of heat radiated by heating element105 is proportionally increased. Therefore, the total amount of heatradiated by the heating element and, consequently, the increase intemperature obtained thereby, is a function of the duration ofenergization of energizable switch means 107.

An exemplary embodiment of apparatus that may be utilized to energizeenergizable switch means 107 is schematically illustrated by the logiccircuit of FIG. 3 and comprises storage means 200, gating means 203, 204and 206, selective gating means 209 and driver means 21 1. Storage means200 is adapted to store a history of the preceding energizations of theheating element included in the fuser assembly 40 illustrated in FIG. 1and, therefore, may comprise a plural stage shift register meansincluding an input terminal for receiving an irregularly occurringselective energizing signal and a shift terminal for receiving aperiodic shift signal. It is recalled that the selective printingapparatus with which the present invention may be utilized is adapted todevelop and transfer an image of a given data card when said card isprovided with scanning information from which is derived a print signal.As described in US. Pat. No. 3,700,324, a derived print signal isshifted through shift register means in timed relation with the rotationof image information obtained from a corre sponding data card. The imageinformation is distributed on the surface of a rotating photosensitivedrum in the form of a distributed electrostatic charge pattern.Accordingly, the relative position of the image information at any giventime may be determined by the particular position occupied by the printsignal as said print signal is shifted through the shift register means.Moreover, once the image information is developed and transferred to aportion of the support base, the movement of that portion may berepresented by a corresponding shifting of the print signal through theshift register means. It should, therefore, be readily apparent that aprint signal will be shifted to a predetermined position within theshift register means when a portion of the support base is advanced tothe fuser assembly. Hence, electroscopic particles that are disposed inimage configuration on the support base are to be fused to the supportbase when a print signal occupies said predetermined position. As willsoon become apparent, the print signal occupying the predeterminedposition need not be associated with that particular portion of thesupport base that is advanced to the fuser assembly. However, except forinitial portions of the support base, each succeeding portion that istransported to the fuser has a powder image disposed thereon. Storagemeans 200, may, therefore, comprise a portion of the aforementionedshift register means having a first stage corresponding to thepredetermined position and including a plurality of succeeding stages.Alternatively, the storage means 200 may comprise an individual pluralstage shift register means having a first stage corresponding to theaforementioned predetermined position and including a plurality ofsucceeding stages. In either case, the storage means is illustrated inFIG. 3 as comprising a plural stage shift register means wherein onlystages 1-8 have been designated as only these stages are of interesthere. As is understood by those of ordinary skill in the art, aconventional shift register is adapted to shift an input signal appliedthereto consecutively through the stages thereof in accordance with atransition in the shift signal applied. The shift register may,therefore, comprise a counter capable of representing timing informationrelating to the times of occurrence of successive input signals inaccordance with the particular stages occupied thereby.

The input terminal of storage means 200 is coupled to terminal 201 towhich is applied a preselected information signal such as theaforementioned print signal. The shift terminal of storage means 200 iscoupled to terminal 202 to which is applied a periodic shift signal. Theperiodic shift signal may be derived from the system clock which isexplained in detail in U.S. Pat. 3,700,324. Accordingly, the periodicshift signal may take the form of clock pulses having a periodcorresponding to the rate at which the data cards are scanned andimaged. The clock pulse period is thus equal to the interval of timerequired to transfer successive developed images from the photosensitivedrum to support base 9. Consequently, the clock pulse period is alsoequal to the interval of time required to translate successive portionsof the support base 9 to the fuser assembly 40.

The outputs of stage 1-8 of storage means 200 are coupled to theillustrated decoding means, which decoding means is adapted to analyzethe sequence of the print signals that have been supplied to storagemeans 200. The decoding means includes first gating means 203, secondgating means 204, third gating means 206 and selective gating means 209.First gating means 203 is comprised of a coincidence means including afirst input terminal coupled to the first stage of storage means 200 anda second input terminal coupled to terminal 202. Coincidence means 203is adapted to produce a signal admitting of a pre-established minimumduration whenever a print signal is applied to terminal 201. It isappreciated, therefore, that the coincidence means is adapted to producean output signal in response to the application of a predeterminedsignal at each input terminal thereofv Accordingly, coincidence means203 may comprise a conventional AND gate whereby a binary I is producedat the output terminal thereof when a binary 1 is supplied to each inputterminal thereof. For the purpose of the present discussion, it will beassumed that a binary l is represented by a positive DC potential and abinary 0" is represented by ground potential. It is, of course,understood that the foregoing binary signals may be represented by anysuitable voltage potentials. Similarly, coincidence means 203 maycomprise a conventional NAND gate whereby a binary 0 is produced at anoutput terminal thereof when a binary l is supplied to each inputterminal thereof.

The second gating means 204 is adapted to sense the expiration of afirst interval of time intermediate successive occurrences of a printsignal and to produce a signal admitting of a second pre-establishedduration in response thereto. The second pre-established duration isgreater than the aforementioned pre-established minimum duration. Moreparticularly, gating means 204 is adapted to detect when more than twoclock pulse periods have expired since the occurrence of the immediatelypreceding print signal. Such expiration corresponds to an elapsed timesince the previous energization of the heating element included in fuserassembly 40 that the fuser assembly has cooled to a temperaturerequiring an energization thereof for a duration longer than the minimumduration to attain a suitable accumulation of radiant energy in theassembly. Second gating means 204 includes a first input terminalcoupled to a given stage, such as the first stage, of storage means 200viia inverting means 205, a second input terminal coupled to a secondstage of storage means 200 and a third input terminal coupled to a thirdstage of storage means 200. An output signal is produced by secondgating means 204 when the first stage of storage means 200 is occupiedby a print signal but the second and third stages, respectively, ofstorage means 200 are not occupied by a print signal. Accordingly,second gating means 204 may comprise a conventional inverting OR, orNOR, circuit wherein a binary l is produced at the output terminalthereof when a binary 0 is applied to each input terminal thereof.Alternatively, the second gating means 204 may comprise a conventionalAND gate, similar to the aforedescribed AND gate 203, wherein a firstinput terminal thereof is coupled directly to the first stage of storagemeans 200 and the second and third input terminals thereof are coupledto the second and third stages, respectively, of storage means 200 viainverting means. The inverting means 205 illustrated herein may comprisea conventional logic negation circuit adapted to produce a binary 0 inresponse to a binary l supplied thereto, and, conversely, to produce abinary l in response to a binary O supplied thereto.

The third gating means 206 is adapted to sense the expiration of asecond interval of time intermediate successive occurrences of the printsignal, the second interval being greater than the aforementioned firstinterval. More particularly, gating means 206 is adapted to detect whenmore than six clock pulse periods have expired since the occurrence ofthe immediately preceding print signal. Should this condition obtain, itis appreciated that the time that has elapsed since the previousenergization of the heating element included in the fuser assembly 40 issufficient to permit cooling of the fuser assembly to a point whereat anextended energization thereof is preferred to achieve a suitableaccumulation of radiant energy therein. It will soon become readilyapparent that the condition precedent to the activation of gating means204 comprises a portion of the conditions precedent to the activation ofgating means 206. Hence, gating means 204 is adapted to produce a signalwhenever the gating means 206 produces a signal. This fact enables asimplification in the construction and interconnection of gating means206 such that the gating means may include a first input terminalcoupled to the second stage of storage means 200 via inverting means207, second through seventh input terminals coupled to stages 3-8,respectively, of storage means 200 and an eighth input terminal coupledto ter minal 202 via inverting means 208. The gating means may comprisea conventional inverting OR, or NOR, circuit similar to NOR circuit 204or, alternatively, an AND gate similar to the AND gate previouslydescribed with respect to gating means 204. It is recognized that ifgating means 206 is constructed of commercially available logiccomponents, an eightinput NOR circuit might not be feasible.Accordingly, the NOR circuit may be comprised of a pair of readilyavailable fourinput NOR circuits having output terminals coupled to aconventional AND gate.

Although not specifically illustrated herein, additional gating means,similar to those just described, may be provided to sense the expirationof other intervals of time intermediate the successive occurrences of aprint signal. Similarly, the interconnections between gating means 206and storage means 200 may adopt any suitable configuration to permit thesensing of the expiration of any corresponding interval of time.

The output terminals of AND gate 203, NOR circuit 204 and NOR circuit206 are coupled to corresponding input terminals of the selective gatingmeans comprised of series connected inverting OR, or NOR, circuit 209and inverting means 210. It is recognized by those of ordinary skill inthe art that the combination of NOR circuit 209 and inverting means 210comprises a conventional OR circuit wherein a binary l is produced atthe output terminal thereof in response to the application of a binary lto any of the input terminals thereof. The OR circuit comprised of NORcircuit 209 and inverting means 210 is connected to conventional drivingmeans 211 which, in turn, is coupled to the energizing coil 212 of aconventional relay. Driving means 211 is adapted to respond to a switchenergizing 'signal applied thereto to supply the energizing coil 212with ground potential. Accordingly, driving means 211 may comprise aconventional transistor means having a base electrode coupled to the ORcircuit comprised of NOR circuit 209 and inverting means 210, acollector electrode coupled to the energizing coil 212 and an emitterelectrode coupled to ground potential. The OR circuit comprised of NORcircuit 209 and inverting means 210 is adapted to selectively couple thesignal admitting of pre-established minimum duration from AND gate 203to drive means 211, the signal admitting of a second pre-establishedduration from NOR circuit 204 to drive means 211 and the signal producedby NOR circuit 206 to drive means 211. The OR circuit acts to combinethe signals produced by NOR circuits 204 and 206 to couple a signaladmitting of a third preestablished duration to drive means 211. It is,of course, now apparent that the OR circuit is capable of coupling thesignals produced by such additional gates that may be provided to drivemeans 211.

The operation of the apparatus illustrated in FIG. 3 will now bedescribed. It is recalled that the successive portions of the supportbase 9 upon which the electroscopic particles are disposed in imageconfiguration are intermittently moved through the fuser assembly 40even though the data cards and photosensitive drum are continuallyadvanced and rotated, respectively. Consequently, it is expected that ifone out of five data cards, for example, are to be printed, only oneprint receiving portion of the support base 9 will be moved through thefuser assembly 40 during the interval required to process the five datacards. Stated otherwise,

only one print signal in the form of a pulse will be applied to terminal201 notwithstanding the application of five clock pulses to terminal202. To facilitate the ready understanding of the instant invention, theexample represented by the timing diagram of FIG. 4, as read in a leftto right configuration, will be assumed. This example is assumed merelyfor purposes of illustration and should not be considered tounnecessarily limit the instant teachings of the invention thereto. Itwill .also be assumed that the fuser assembly and printing apparatusoperatively associated therewith has been in operation for some time. Atthe first timing period under consideration, i.e., at timing pulse 1 ofwaveform 202', the first print signal, represented by the first pulse atthe left-hand portion of waveform 201, is applied to terminal 201. It isseen that this first pulse 201 represents that a portion of the supportbase 9 has been advanced to the fuser assembly 40, the heating elementincluded in the fuser assembly must now be energized to attain atemperature sufficient to achieve the fixing of theelectroscopicparticles to the support base and the heating element has not beenenergized since the last occurrence of the immediately preceding pulse20l',not shown. Thus, at clock pulse 1, the print signal is shifted intothe first stage of storage means 200 and stages 2-8 thereof are notprovided with print signals. The storage means 200 may be responsive tothe positive transition of the clock pulses 202' applied thereto. Ofcourse, the negative transitions of the clock pulses may be utilized toshift applied signals through the storage means, if so desired.Accordingly, AND gate 203 is supplied with a binary l by the first stageof storage means 200 and with a binary l by clock pulse 1 applied toterminal 202 to produce a first energizing signal admitting of aduration equal to the duration of clock pulse 1 as illustrated bywaveform 203'. Similarly, NOR circuit 204 is supplied with a binary O bythe second and third stages, respectively, of storage means 200 and,after the inversion of the binary l stored in the first stage of storagemeans 200, with a binary 0 by inverting means 205 to produce anenergizing signal admitting of a duration equal to the clock pulseperiod, as represented by waveform 204'. It is apparent that theenergizing signal produced by NOR circuit 204 represents that more thantwo clock pulse periods have expired since the occurrence of theimmediately preceding print signal. Thus, at clock pulse 1, the ORcircuit comprised of NOR circuit 209 and inverting means 210 responds tothe energizing signals applied thereto by AND gate 203 and NOR circuit204 to supply driver means 21 1 with a switch energizing signaladmitting of a duration corresponding to that exhibited by waveform204'. This switch energizing signal, represented by waveform 210' andaligned with clock pulse 1, activates driver means 211 which, in turn,energizes the energizing coil 212 for a period of time equal to oneclock pulse period. Hence, during-this period, current.

flows from the source of energizing potential +V through energizing coil212 to ground potential applied to the energizing coil by driver means211. Consequently, switch means 107 of FIG. 2A is activated and therebyopened, for a corresponding period of time. For the purpose ofillustration, it will be assumed that one clock pulse period admits of aduration equal to approximately 332 milliseconds, the width of a clockpulse is approximately 230 milliseconds and the frequency of the ACwaveform 120 illustrated in FIG. 2B is approximately 60hz. Theactivation of switch means 107 for a duration of approximately 332milliseconds will enable bidirectional current conducting means 101 tooperate upon approximately 20 cycles of the AC voltage applied theretoto supply heating element 105 with a sufficiently high RMS voltage. Theelectroscopic particles disposed in image configuration upon the supportbase 9 will, therefore, be fused thereto. However, since the fuserassembly 40 had not been previously energized for a prolonged period oftime, the heating element therein has cooled to a lower quiescenttemperature. It is, therefore, preferred that the heating element beenergized for a further duration to permit the fuser assembly toaccumulate additional radiant energy whereby a higher temperature isattained. Accordingly, at clock pulse 2, the print signal stored in thefirst stage of storage means 200 is shifted into the second stagethereof. This print signal pulse is inverted by inverting means 207 andthe first seven input terminals of NOR circuit 206 are each suppliedwith a binary Clock pulse 2 is inverted by inverting means 208 and theeighth input terminal of NOR circuit 206 is also supplied with a binary0. The signal thus produced by NOR circuit 206, depicted by the waveform206' in alignment with clock pulse 2, admits of a duration equal to theclock pulse duration and is applied to driver means 211. It isrecognized that the signal produced by NOR circuit 206 represents thatmore than six clock pulse periods have expired since the occurrence ofthe immediately preceding print signal. Switch means 107 is thusactivated for an additional 230 milliseconds (the approximate clockpulse duration) during the immediately succeeding clock pulse period. Itmay thus be observed that the switch energizing signal produced by theOR circuit comprised of NOR circuit 209 and inverting means 210, andrepresented by the waveform 210 is effective to energize the heatingelement of the fuser assembly for one complete clock pulse period andfor one additional clock pulse duration.

It is apparent from waveform 201, that at clock pulse 2 a print signalis not applied to terminal 201. Hence, the next successive portion ofthe support base 9 is not moved through the fuser assembly 40. This, ofcourse, means that the image information derived from the data cardcorresponding to clock pulse 2 is not to be printed. Nevertheless, itshould be noted that the additional energization of the heating elementof the fuser assembly during the second clock pulse period, as justdescribed hereinabove, is not sufficient to scorch or otherwise damagethe support base that extends within the fuser assembly. Moreover, ifthe support base has been advanced at clock pulse 2, the additionalenergization of the heating element would be advantageously utilized tofix the next successive developed image to the support base. At clockpulse 3, terminal 201 is not provided with a print signal and,therefore, the fuser assembly 40 need not be energized. In addition, atthis time, the first print signal that had been applied to terminal 201is shifted into the third stage of storage means 200. Similarly, atclock pulse 4, that print signal is shifted into the fourth stage ofstorage means 200.

Waveform 201 indicates that the next successive print signal pulse isapplied to terminal 201 during clock pulse period 5. At this time, theimmediately preceding print signal is shifted into the fifth stage ofstorage means 200. Hence, approximately 1328 milliseconds (i.e., fourclock pulse periods) have elapsed since a given portion of the supportbase 9 was moved into the fuser assembly 40. Moreover, approximately 766milliseconds have elapsed since the energization of the heating elementof the fuser assembly 40 was terminated. The fuser assembly has,therefore, cooled such that the accumulated energy therein hasdissipated below the fusing level. At clock pulse 5, AND gate 203produces a signal illustrated by waveform 203', which signal is appliedto the OR circuit comprised of NOR circuit 209 and inverting means 210.In addition, NOR circuit 204 responds to each binary 0 applied theretoby the second and third stages, respectively, of storage means 200 andto the binary 0 applied thereto by inverting means 205. It is, ofcourse, appreciated that the print signal occupying the first stage ofstorage means 200 is subjected to a logic negation by inverting means205 to produce the last mentioned binary 0. Accordingly, a signalrepresented by the waveform 204' and admitting of a duration equal to aclock pulse period is also applied to the OR circuit comprised or NORcircuit 209 and inverting means 210. Consequently, at clock pulse 5, theswitch energizing signal, represented by waveform 210' is applied todriver means 211 whereby switch means 107 is activated. The activationof switch means 107 results in the energization of the heating elementincluded in the fuser assembly 40 for a duration equal to one clockpulse period. The electroscopic particles disposed on the support base 9in image configuration are thus fused on the support base. Furthermore,the energizing duration of approximately 332 milliseconds is sufficientto enable the fuser assembly to attain a desirably high temperature,thus accumulating an adequate amount of radiant energy.

A print signal is not applied to terminal 201 at the next clock pulseperiod 6 and, therefore, further movement of the support base 9 isinterrupted. Thus, that portion of the support base that was previouslyadvanced into the fuser assembly 40 remains therein and the accumulatedradiant energy serves to properly complete the fusing operation. Inaddition, at clock pulse 6, a binary O is shifted into the first stageof storage means 200 and the previous print signal is shifted into thesecond stage of storage means 200. Accordingly, AND gate 203 and NORcircuit 204 are each disabled and thus do not produce output signals.Although the print signal stored in the second stage of storage means200 is inverted by inverting means 207 and applied as a binary 0 to NORcircuit 206, it is observed that the first print signal has now beenshifted to the sixth stage of storage means 200 and, therefore, NORcircuit 206 is also disabled from producing a pulse signal. This, ofcourse, is expected since not more than six clock pulse periods haveelapsed intermediate the first and second print signal times ofoccurrence. The next succeeding print signal is applied to terminal 201at clock pulse 8 and is shifted into the first stage of storage means200 as indicated by the waveform 201'. Hence, three clock pulse periodshave elapsed since the immediately preceding print signal was applied toterminal 201 and approximately 664 milliseconds have elapsed since theenergization of the heating element included in the fuser assembly wasterminated. At clock pulse 8, the immediately preceding print signal isshifted into the fourth stage of storage means 200 and the first printsignal is shifted into the eighth stage of storage means 200.Accordingly, AND gate 203 responds to the print signal applied to itsfirst input terminal and to the clock pulse applied to its second inputterminal to produce the signal represented by waveform 203 admitting ofa clock pulse duration. Additionally, the elapsed time betweensuccessive print signals exceeds two clock pulse periods and NOR circuitthe waveform 204' admitting of a duration equal to the clock pulseperiod. Nor circuit 206 is inhibited from producing an output becausethe first print signal is applied to an input terminal thereof by theeighth stage of storage means 200. The OR circuit comprised of NORcircuit 209 andinverting means 210 responds to the signalsappliedtheretoby AND gate 203 and NOR circuit 204 to apply'a switch energizing signalrepresented by the waveform 210' to driver means 211. Switch means107'is, therefore, activated for a duration equal to a clock pulseperiod, thereby energizing the heating element 105 included in the fuserassembly 40. Consequently, the electroscopic particles disposed inconfiguration upon the third successive portion of the support base 9are fused thereto. I

At clock pulse 9 an immediately succeeding print signal is applied toterminal 201, thereby representing that the support base 9 is advancedthrough fuser assembly 40 to expose the next successive portion of thesupport base to a fusing operation. It is, therefore, appreciated thatthe image information derived from consecutive data cards are to beprinted. Hence, at clock pulse 9 the first'and secondstages of storagemeans 200 are each occupied by a print signal, the fifth stage ofstorage means 200 is occupied by a print signal and the remaining stagesof storage means 200 are not provided with print signalspltis,therefore, appreciated that only AND gate 203is activated to produce anoutput signal represented by the waveform 203', which signal is appliedby the OR circuit comprised of NOR circuit 209 and inverting means 210as a switch energizing signal 210" to driver means 211. Thus, switchmeans 107 is activated for a duration equal to a clock pulse duration 91 thereby energizing the heating element included in the fuser assembly40. As may be observed from waveform 210', the activation of switchmeans 107 for an entire clock pulse period during the immediatelypreceding 'clock pulse period eight and the activation of switch means107 for a clock pulse duration during the clock pulse period 9 issufficient to maintain the energization of the heating element for atotal time interval of approximately 562 inilliseconds. Hence,sufficient heat is applied to the electroscopic particles disposed inimage 1 v configuration on support base 9 to fuse said particles to thesupport base. Thus, the printed images derived from the successive datacards are suitably fixed to the means 200. It is therefore appreciatedthat an output signal is not produced by any of AND gate 203, NORcircuit 204 or NOR circuit 206. However, at clock pulse 11, a printsignal is applied to terminal 201 and shifted into the first stage ofstorage means 200 as represented by waveforms 201'. At clock pulse 11,the third stage of storage means 200 is occupied by the immediatelypreceding print signal, the fourth stage of storage means 200 isoccupied by the next preceding print signal and the seventh stage ofstorage means 200 is occupied by the third preceding print signal.Hence, only and gate 203 produces an output signal, represented bywaveform 203' which, it is appreciated, admits of a duration equal to aclock pulse duration. The signal produced by AND gate 203 is applied asa switch energizing signal to driver means 211 by the OR circuitcomprised of NOR circuit 209 and inverting means 210 as represented bythe waveform 210. Consequently, switch means 107 is activated for thepre-established minimum duration to thereby energize theheating elementincluded in the fuser assembly 40 for a corresponding duration.

During the next succeeding clock pulse periods, the image informationrotating on the photosensitive drum is not printed and, therefore, aprint signal pulse is not applied to terminal 201, the support base 9 isnot advanced through the fuser assembly 40 and the heating elementincluded in the fuser assembly is not energized. However, at clock pulse18 image information derived from a data card and transferred to thesupport base 9 is to be fixed to the support base. Accordingly a portionof the support base upon which electroscopic particles are disposed inimage configuration is advanced to the fuser assembly 40 and a printsignal is applied to terminal 201 and shifted into storage means 200 asrepresented by waveform 201'. None of the second to seventh stages ofstorage means 200 is occupied by a print signal but the immediatelypreceding print signal (i.e., the print signal that occurred at clockpulse 11) occupies the eighth stage of the storage means. Consequently,both AND gate 203 and NOR circuit 204 produce output signals representedby the waveforms 203' and 204', respectively. These signals are appliedas a switch energizing signal to drive means 21 l by the OR circuitcomprised of NOR circuit 209 and inverting means 210 as represented bythe waveform 210'. Switch means 107 is thus activated for a durationequal to a clock pulse period, thereby energizing the heating elementfor a corresponding duration.

It is observed that more than six clock pulse periods (viz. seven clockpulse periods) have elapsed since the occurrence of the immediatelypreceding print signal. Also, more than six clock pulse periods haveelapsed since the termination of the immediately preceding energizationof heating element 105. Hence, heating element 105, which has cooled toa lower quiescent temperature, must be energized for an additionalperiod of time to enable sufficient radiant energy to accumulate in thefuser assembly 40. Thus, at clock pulse 19, the immediately precedingprint signal is shifted into the second stage of storage means 200 andthe third through eighth stages of the storage means are not providedwith stored print signals. Accordingly, NOR circuit 206 is activated toproduce an output signal 206, admitting of a duration equal to a clockpulse duration, which pulse is applied as a switch energizing signal tothe driver means 211 by the OR circuit comprised of NOR circuit 209 andinverting means 210. Switch means 107 is thus activated for anadditional interval during clock pulse period 19 to'effect the requiredadditional energization of heating element 105.

At clock pulse 20 the last preceding print signal is shifted into thethird stage of storage means 200 and at clock pulse 21 another printsignal is applied to terminal 201 and shifted into storage means 200 asrepresented by the waveform 201. It is appreciated that more than twoclock pulse periods have elapsed since the occurrence of the immediatelypreceding print signal and, in addition, more than approximately 434milliseconds have expired since the immediately preceding energizationof heating element 105 has terminated. Thus the proper fusing of theelectroscopic particles disposed in image configuration on support base9 requires slightly more than the pre-established minimum duration ofenergization of the heating element. Consequently, at clock pulse 21 thefirst stage of storage means 200 is occupied by the print signalrepresented by waveform 201 and neither the second nor third stages ofthe storage means is occupied by a print signal. Hence, an output signalrepresented by waveform 203 is produced by AND gate 203 and an outputsignal represented by waveform 204' is produced by NOR circuit 204. TheOR circuit comprised of NOR circuit 209 and inverting means 210 respondsto the signals applied thereto to apply a switch energizing signalrepresented bywaveform 210' to driver means 211. Accordingly, switchmeans 107 is activated for a duration equal to a clock pulse period,thereby energizing the heating element 105 for a corresponding intervalof time.

It should now be fully appreciated from the foregoing descriptionthereof that storage means 200 stores the time related history of themovement of successive portions of support base 9 through the fuserassembly 40. Clearly, a variable time interval may elapse betweenconsecutive movements. This, of course, is represented by the selectedstages of storage means 200 which are occupied by print signals.Moreover, since the energization of the heating element of the fuserassembly is dependent upon the application of a print signal to terminal201, the selected stages of storage means 200 that are occupied by printsignals provide an indication of the length of time that has expiredbetween successive energizations of the heating element.

In the description of FIG. 3, it has been assumed that conventional,commercially available TTL logic is utilized throughout for each of theAND gates, NOR circuits, inverting means, storage means and drivermeans. However, any of the specific, logic components or arrangementsmay be replaced by other components or groups thereof which producesimilar output signals in response to corresponding input conditions.Also, the precise mode of logic operation employed thereby may differfrom that described hereinabove in a matter that is obvious to those ofordinary skill in the art. Furthermore, the logic circuit illustrated inFIG. 3 may, alternatively, be implemented by MSI logic, individualcircuit components or MOS circuit chips. In addition, the variablesupply 100 illustrated in FIG. 2A may be replaced by other conventionalsources of energy sufficient to supply the heating element with anincreased voltage in response to a switch energizing sig- 6 nal producedby the OR circuit comprised of NOR circoupled to heating element 105through conventional switching means, the latter being adapted to beactivated in response to the switch energizing signal produced by theaforementioned OR circuit. Moreover, the heating element 105 need not belimited merely to a conventional quartz lamp, but, alternatively, may

comprise any suitable heat radiating device or other heating deviceconventionally utilized in fuser assemblies or other electroscopicparticle fixing devices.

While the invention has been particularly shown and described withreference to an exemplary embodiment thereof, it will be obvious tothose skilled in mean that various changes and modifications in form anddetails may be made without departing from the spirit and scope of theinvention. Thus,'the specific numerical examples described hereinaboveare intended to be merely illustrative of the operation of the apparatusdisclosed herein and are not intended to limit the teachings of-theinstant invention. Accordingly, any suitable clock pulse period andclock pulse duration may be employed herewith. Moreover, storage means200 may comprise any conventional storage device capable of storing asuitable history of the previous operation of the fuser assembly and,therefore, of the intermittently moving support base. NOR circuit 204may be adapted to produce an output signal if three or more clock pulseperiods have expired since the occurrence of the immediately precedingprint signal. Similarly, NOR circuit 206 may be adapted to produce anoutput signal when any other convenientnumber of clock pulse periodshave expired since the occurrence of an immediately preceding printsignal. And additional gating means may be provided to produce outputsignals upon detecting the expiration of other clock pulse periods. itis, of course, recognized that these NOR circuits and gating means may,therefore, produce output signals admitting of any desired duration toenergize the heating element of the fuser assembly in accordance withthe particular interval of time that has expired since the immediatelypreceding energization of the heating element. Thus, it is intended thatthe appended claims be interpreted as including the foregoing as well asother obvious changes and modifications.

What is claimed is: l. A method of regulating the operation of a fuserassembly in accordance with selected information requiring theenergization of said fuser assembly wherein the selected information isprovided by a plurality of preselected information signals, said signalsbeing spaced in time, and wherein the radiant energy accumulated by saidfuser assembly is a function of the expiration of time from animmediately preceding energization thereof, comprising the steps of:

sensing the occurrence of a preselected information signal to energizesaid fuser assembly for a preestablished minimum period of time; and

energizing said fuser assembly for a period of time that is dependentupon the interval of time that has expired immediately prior to theoccurrences of the sensed preselected information signal without theoccurrence of one of said plurality of preselected information signals.

2. The method of claim 1 wherein said fuser assembly is energized uponsensing the respective occurrences of the succeeding ones of thesuccessive preselected information signals.

3. The method of claim 2 wherein said step of sensing the occurrence ofa preselected signal comprises'the steps of:

serially storing each preselected information signal and the number ofpredetermined time durations separating successive ones of saidpreselected information signals in consecutive order; and

generating a first energizing signal admitting of said I pre-establishedminimum period of time when a preselected information signal is storedin a first position of said consecutive order.

4. The method of claim 3 wherein said step of energizing said fuserassembly comprises the step of generating a second energizing signalwhen a preselected information signal is stored in a first position ofsaid'consecutive order and a number of predetermined time'durations arestored in the next successive positions of said consecutive order, saidsecond energizing signal admitting of a period of time that is afunction of said number of successively stored predetermined timedurations.

5. A method of regulating the operation of a fuser assembly inaccordance with selected information requiring the energization of saidfuser assembly wherein the selected information is provided by aplurality of preselected information signals, said signals being spacedin time, and wherein the heat accumulated by said fuser assembly is afunction of the expiration of time from an immediately precedingenergization thereof, comprising the steps of:

serially storing each preselected information signal and the number ofpredetermined time durations separating successive ones of saidpreselected inlected information signal is stored in a first position ofsaid consecutive order; generating a second energizing signal admittingof a second pre-established period of time when a preselectedinformation signal is stored in a first position of said consecutiveorder and a first selected number of predetermined time durations arestored in the next successive positions of said consecutive order;generating a third energizing signal admitting of said pre-establishedminimum period of time when a preselected information signal is storedin a second position of said consecutive order and a second selectednumber of predetermined time durations are stored in the next successivepositions of said consecutive order; and selectively energizing saidfuser assembly in response to said first, second and third energizingsignals. 6. The method of claim 5 wherein said fuser assembly isenergized for said pre-established minimum period of time when only saidfirst energizing signal is generated, said fuser assembly is energizedfor said second preestablished period of time when only said first andsecond energizing signals are generated and said fuser assembly isenergized for a third pre-established period of time when said first,second and third energizing signals are all generated.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 13,916,146 D October 28, 1975 I INVENTOMS) 1 Mark A. Hutner It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

On the title page, Col. 1, line 3, after Assignee, replace "WestinghouseElectric Corporation, Pittsburgh, Pa." with-Xerox Corporation, Stamford,

Conn.

Signed and Scaled this Twentieth Day of July 1976 [SEAL] A ttes t:

RUTH C. MASON C. MARSHALL DANN Atrestr'ng Officer Commissioner uj'Paremsand Trademarks UNITED STATES PATENT OFFICE QERTIFICATE 0F CORRECTIONPATENT NO. 1 3,916,146 DATED I October 28, 1975 INVENT0R(5) 1 Mark A.Hutner It is certified that error appears in the above-identified patentand that said Letters Patent are hereby corrected as shown below:

On the title page, Col. 1, line 3, after Assignee, replace "WestinghouseElectric Corporation, Pittsburgh, Pa."'with-Xerox Corporation, Stamford,

Conn.-

Signed and Sealed this Twentieth Day of July 1976 [SEAL] A ttes t:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner oj'Parentsand Trademarks

1. A method of regulating the operation of a fuser assembly inaccordance with selected information requiring the energization of saidfuser assembly wherein the selected information is provided by aplurality of preselected information signals, said signals being spacedin time, and wherein the radiant energy accumulated by said fuserassembly is a function of the expiration of time from an immediatelypreceding energization thereof, comprising the steps of: sensing theoccurrence of a preselected information signal to energize said fuserassembly for a pre-established minimum period of time; and energizingsaid fuser assembly for a period of time that is dependent upon theinterval of time that has expired immediately prior to the occurrencesof the sensed preselected information signal without the occurrence ofone of said plurality of preselected information signals.
 2. The methodof claim 1 wherein said fuser assembly is energized upon sensing therespective occurrences of the succeeding ones of the successivepreselected information signals.
 3. The method of claim 2 wherein saidstep of sensing the occurrence of a preselected signal comprises thesteps of: serially storing each preselected information signal and thenumber of predetermined time durations separating successive ones ofsaid preselected information signals in consecutive order; andgenerating a first energizing signal admitting of said pre-establishedminimum period of time when a preselected information signal is storedin a first position of said consecutive order.
 4. The method of claim 3wherein said step of energizing said fuser assembly comprises the stepof generating a second energizing signal when a preselected informationsignal is stored in a first position of said consecutive order and anumber of predetermined time durations are stored in the next successivepositions of said consecutive order, said second energizing signaladmitting of a period of time that is a function of said number ofsuccessively stored predetermined time durations.
 5. A method ofregulating the operation of a fuser assembly in accordance with selectedinformation requiring the energization of said fuser assembly whereinthe selected information is provided by a plurality of preselectedinformation signals, said signals being spaced in time, and wherein theheat accumulated by said fuser assembly is a function of the expirationof time from an immediately preceding energization thereof, comprisingthe steps of: serially storing each preselected information signal andthe number of predetermined time durations separating successive ones ofsaid preselected information signals in consecutive order; generating afirst energizing signal admitting of a pre-established minimum period oftime when a preselected information signal is stored in a first positionof said consecutive order; generating a second energizing signaladmitting of a second pre-established period of time when a preselectedinformation signal is stored in a first position of said consecutiveorder and a first selected number of predetermined time durations arestored in the next successive positions of said consecutive order;generating a third energizing signal admitting of said pre-establishedminimum period of time when a preselected information signal is storedin a second position of said consecutive order and a second selectednumber of predetermined time durations are stored in the next successivepositions of said consecutive order; and selectively energizing saidfuser assembly in response to said first, second and third energizingsignals.
 6. The method of claim 5 wherein said fuser assembly isenergized for said pre-established minimum period of time when only saidfirst energizing signal is generated, said fuser assembly is energizedfor said second pre-established period of time when only said first andsecond energizing signals are generated and said fuser assembly isenergized for a third pre-established period of time when said first,second and third energizing signals are all generated.